1. Field of the Invention
Embodiments of the present invention generally relate to downhole production operations and particularly to inflatable tools used in such operations.
2. Description of the Related Art
Inflatable elements, such as inflatable packers and plugs, are commonly used in downhole production operations. The inflatable elements are typically inflated with wellbore fluids, or transported inflation fluids, via an inflation tool. The inflation tool may include a single or multi-stage downhole pump capable of drawing in wellbore fluids, filtering the fluids, and injecting the filtered fluids into the inflatable element. The inflatable element typically includes an inflatable section made of one or more elastomers. When the inflatable element is filled with fluids, the elastomers expand and conform to a shape and size of the wellbore or casing, thus creating a seal to isolate an area of the wellbore.
The inflation tool is typically operated via electricity supplied from a surface power supply via an electric cable, or “wireline.” An operator at the surface may monitor voltage supplied to the inflation tool and current draw of the inflation tool to verify pump operations and to estimate the output pressure of the tool. For example, voltage supplied to the inflation tool and current draw of the inflation tool may be proportional to pump speed and pressure output, respectively. This data is typically collected at the surface from the power supply without any type of direct communication with the inflation tool. Downhole conditions, such as downhole temperature and pressure are typically not monitored while running and setting the inflatable element with the inflation tool.
However, downhole pressure and temperature can have a marked affect on the performance of an inflatable packer or plug. For example, the elastomers typically have very specific operating temperature ranges. If exposed to excessive temperature, the elastomers may degrade. A traditional approach to determine conditions in the wellbore, such as downhole temperature, prior to setting an inflatable element, is by prediction using historical data. For example, the temperature of the wellbore at the setting depth may be predicted from data from a previous logging run. However, because this approach may fail to properly account for changes in downhole conditions subsequent to the previous logging run, accuracy of these predictions may be limited.
Furthermore, inflatable products exposed to temperature excursions can experience broad variations of internal pressure after the tool has been set. In fact, it has been reported that the single-most cause of failure of inflatable products is a change in temperature after the tool has been set. The decision to use a thermal compensator, a mechanical device to compensate for the volume change of the inflation fluid due to temperature, may be based on the initial temperature at the setting depth and an estimation of the temperature excursion caused by events, such as producing the well or injecting treating fluids into the well. A traditional approach to estimating the temperature excursion is by using complex software techniques for modeling these events. However, due to complexity in modeling these events and the previously described uncertainty in establishing the initial temperature, the accuracy of these predictions are limited, as well.
One approach to increase a confidence in these predictions is to run sensors with the inflation tool to log data while setting the inflatable element. The data may be retrieved later to determine the accuracy of the estimates. However, this approach does not prevent damage to a tool in case well conditions are outside the operating ranges of the inflatable element.
Accordingly, what is needed is an improved method and apparatus for monitoring downhole conditions prior to, during, and after setting an inflatable element.